1. Field of the Invention
The present invention relates to a switch with pre-alarm means for generating an alarm when an abnormal current flows through a breaker of the switch prior to an actual tripping operation of the breaker, and specially to a switch with pre-alarm means to be used for measuring an effective value of the current flowing in the breaker or in the load by using the pre-alarm function thereof.
2. Description of the Prior Art
For measuring the value of current flowing in breaker of a switch, an ammeter or a current transformer, which is clamped or disposed on electric power lines or breaker of the switch, has been conventionally used. In the conventional measurement, generally the peak value of the current has been measured. Also for specifically measuring the effective value of the current, a circuit for measuring the effective value needs to be provided on tripping circuit of the switch.
As mentioned-above, since a complex apparatus or means must be used in the conventional switch for measuring the current on the breaker or the load, there is a demand for measuring the current value flowing on the load easily without using such complex apparatus.